[Br:1][CH2:2][CH:3]([OH:13])[CH2:4][P:5](=[O:12])([O:9][CH2:10][CH3:11])[O:6][CH2:7][CH3:8].[O:14]1[CH:19]=[CH:18][CH2:17][CH2:16][CH2:15]1>C(OCC)(=O)C.C1(C)C=CC(S(O)(=O)=O)=CC=1>[Br:1][CH2:2][CH:3]([O:13][CH:15]1[CH2:16][CH2:17][CH2:18][CH2:19][O:14]1)[CH2:4][P:5](=[O:12])([O:6][CH2:7][CH3:8])[O:9][CH2:10][CH3:11]To a mixture of diethyl 3-bromo-2-hydroxypropylphosphonate (82.5 g) and p-toluenesulfonic acid (1.03 g) was added dropwise 3,4-dihydro-2H-pyrane (250 g) under ice-cooling and with stirring. After the reaction mixture was stirred at the same temperature for 10 minutes and at ambient temperature for 1.5 hours, the dihydropyrane was removed off by evaporation under reduced pressure to give a residue, which was dissolved in ethyl acetate (500 ml). The ethyl acetate solution was washed with saturated aqueous sodium bicarbonate solution (100 ml) and with saturated aqueous sodium chloride solution (100 ml) dried over magnesium sulfate and evaporated to dryness under reduced pressure to give oily diethyl 3-bromo-2-(tetrahydro-2H-pyran-2-yloxy)propylphosphonate (138 g).
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